The present invention relates to absorbent articles.
A various assortment of absorbent articles, such as disposable diapers and sanitary napkins, have been proposed for absorbing and retaining body fluids. Such articles have been constructed with an absorbent pad having a relatively large volume of pad material, in order to provide the necessary absorbency and fluid holding capacity for the articles, which add an undesired bulk to the articles. For example, disposable diapers are commonly made from a fluid impervious backing sheet, a fluid pervious cover sheet, and an absorbent pad, such as comminuted wood pulp known in the art as wood fluff, located between the backing and cover sheets. The pads of such conventional diapers are relatively bulky, particularly in the crotch region, resulting in a poor fit and minimal comfort to the infant.
More recently, it has been proposed to include highly absorbent materials, such as hydrocolloid polymers, in the pads. In theory, the hydrocolloid materials permit a reduction in pad bulk while increasing desirable absorbent and fluid holding characteristics of the pads, since such materials are capable of absorbing and retaining many times their weight in liquid, such as urine or other body fluids. In practice, use of such materials in absorbent articles has been limited due to numerous difficulties caused by the nature of the materials.
Initially, it is preferred that the hydrocolloid materials be utilized in a particulate form, such as granules or flakes, since the particles provide a greater exposed surface area for increased absorbency. However, it has been found that when placed in the pad, the particles migrate in the pad before the article has been used by the wearer. Particle migration may take place during packaging, storage, transportation, or other handling of the articles, and results in movement of the particles from their initial location to remote parts of the pad where they are less effective.
When wetted, the hydrocolloid materials swell and become gelatinous, and assume a slippery or slimy texture which is unstable. As a result, the materials migrate further in the pad when wetted, and cause the pad to become unstable. Thus, it has been found that the wetted materials cause the pads to shift, ball, split and shred during use of the articles. Further, certain of the wetted hydrocolloid materials may be somewhat irritating to the skin, and it is thus desirable to minimize contact of the materials with the skin.